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Study of Baby Teeth Sees Radiation Effects

Men who grew up in the St. Louis area in the early 1960s and died of cancer by middle age had more than twice as much radioactive strontium in their baby teeth as men born in the same area at the same time who are still living, according to a study based on teeth collected years ago by Washington University in St. Louis.

The study, published on Dec. 1 in The International Journal of Health Services, analyzed baby teeth collected during the era when the United States and the Soviet Union were conducting nuclear bomb tests in the atmosphere. The study seeks to help scientists determine the health effects of small radiation doses, and to say how many people died from bomb fallout. There is very little reliable data on the relationship of radiation to cancer at low doses, so scientists instead use extrapolations from higher doses, which introduces large uncertainties into their calculations.

The study implies that deaths from bomb fallout globally run into the “many thousands,” said the authors, Joseph J. Mangano and Dr. Janette D. Sherman, both of the Radiation and Public Health Project, nonprofit research group based in New York.

However, a scientist with long experience in the issue, Kevin D. Crowley, the senior board director of the Nuclear and Radiation Studies Board at the National Research Council, urged caution in interpreting the findings.

“It sounds like the best you could do is say this is an association,” he said. “An association is not necessarily causative.”

R. William Field, an epidemiologist at the University of Iowa, praised the authors for exploring the association between fallout in teeth and cancer, but he that said the sample size was too small and that the study had other limitations. He called for follow-ups.

The study’s authors had previously tried to link strontium in the teeth of children growing up near nuclear power plants to releases from those plants, but those findings have not met with much scientific acceptance. Strontium levels in a person’s body may have more to do with where the person’s food was farmed than with where the person lives. In addition, the Nuclear Regulatory Commission calculated that the doses from radioactive strontium in the environment add only about 0.3 percent to the average American’s background exposure.

But this study tries to link differences in tooth contamination more directly with health outcomes. The study measured the ratio of calcium, a basic building block of teeth and bones, to strontium 90, which is absorbed just as calcium is. The authors said they were using strontium as a proxy for all long-lived fallout components, and they picked boys born in a period when there was a lull in atmospheric testing, so that the boys’ exposure to short-lived radioactive materials, in utero or in the first few months of life, was minimized. They limited their research to boys because men seldom change their names and thus were easier to trace.

The authors found that among 3,000 tooth donors, born in 1959, 1960 or the first half of 1961, 84 had died, 12 of those from cancer. The authors selected two “control” cases, people still living, for each of those who had died. The controls were born in the same county, within 40 days of the person who later died. The study compared incisors with incisors, and molars with molars.

The people who would later die of cancer had an average of 7.0 picocuries of per gram of tooth; the control cases, who have never had cancer, had an average of 3.1 picocuries per gram.

But the picture is not completely clear. Measurements of the teeth of people who later had cancer but survived it did not show strontium levels markedly different from those who had never had cancer, according to the study. One reason may be that those nonfatal cancers were often polyps and melanomas not related to radiation.

A version of this article appears in print on December 14, 2010, on page D2 of the New York edition with the headline: Study of Baby Teeth Sees Radiation Effects. Order Reprints|Today's Paper|Subscribe